Summary Gene transcription signaling through RhoA- and actin-regulated transcription factors plays a critical role in diverse diseases such as cancer and fibrosis. Transcription factors downstream of RhoA and actin, serum response factor (SRF) and myocardin-related transcription factor (MRTF) controls cell proliferation, cancer cell migration and metastasis and the myofibroblast activation. We identified MRTF-pathway inhibitor compounds (e.g. CCG-1423 and CCG-203971) and recently identified the redox-sensitive nuclear protein pirin as a molecular target. This reveals pirin as a regulator of MRTF/SRF- and NFkB-regulated gene transcription providing a novel dual inhibitor mechanism for our CCG compounds relevant to cancer and fibrotic diseases by blocking both inflammatory and pro-fibrotic/proliferative signals. The overarching goal of this work is to explore the role of pirin and the mechanisms of CCG compounds in regulating gene transcription. The specific goals of this renewal application are to explore pirin?s actions on gene transcription regulated by RhoA/MRTF/SRF and NF?B and to define the pirin-dependent and potentially pirin- independent molecular mechanisms of action of the CCG compounds. To accomplish this goal, we will address the following specific aims: Aim 1 Elucidate biochemically, pirin?s interactions with MRTF, SRF, p65, and their DNA complexes with a focus on the role of pirin redox state and the effects of pirin-modulating compounds on these mechanisms. Aim 2 Assess the role of pirin and the effects of CCG compounds in pro-fibrotic and inflammatory gene transcription mediated by MRTF/SRF, TGF-?, Toll-like receptors (TLRs), and NF?B by use of a novel pirin knock- out mouse model. Impact - Successful completion of these aims will reveal mechanisms and scope of gene regulation by pirin and how this may be influenced by the redox environment. It will also provide a mechanistic framework for future development of CCG compounds for clinical use in cancer and fibrotic diseases.